Impact of organic and conventional practices on, soil health and crop yield under tropical and subtropical environment of Bangladesh

In the last four decades Organic Farming (OF) has increased substantially around the world including small holding countries of Asia and Africa (Willer and Lernoud 2015.). The aim of of is to produce safe food in sufficient quantity while being environmental friendly and attain sustainability. Being a tropical and subtropical country like Bangladesh, the major challenges for OF are yield of crops, optimization of the nutrients cycling of the agro-ecosystem and development of more suitable alternative soil fertility strategies. Soil organic matter (SOM) is a key indicator of fertility; affects crop growth and yield, either directly by supplying nutrients or indirectly by modifying the soil physical properties, thereby improving the root environment and, thus, stimulating plant growth(Chang, et al 2007). Pimental, et al. 2005 indicated that the highest total aerial dry matter and grain yields were associated with the highest organic matter contents of the soils. In addition, crop production based on the use of organic manures rather than chemical fertilizers is assumed to be a more sustainable type of agriculture. In recent years, the application of organic fertilizer has received great attention from environmentalists, agriculturists and consumers alike (Chang, et al., 2007). Gabriel et al., 2010 found that depending on crops, soil and weather conditions, organically managed crops yields on a per ha basis was equal to those from conventional agriculture. Organic farming has become very popular and is steadily increasing the area of production around the globe and possesses the highest in Asia. For growing vegetable crops organically, it is required an adequate and continuous supply of essential nutrients for proper growth and maximal high quality yields. But, low yields associate to starvation of plants from slow releasing organic fertlizers, difficulties in weed control, and cumbersome pest management methods are the main concern against organic agriculture. Ponisio et al 2014 to their meta analysis showed that organic yields are only 19.2% (+3.7%) lower than conventional yields, a smaller yield gap than previous estimates and effects of crop types and management practices on the yield gap, two agricultural diversification practices, multi-cropping and crop rotations, substantially reduce the yield gap (to 9+4% and 8+5%, respectively) when the methods were applied in only organic systems. The nutrients released after the biological breakdown of the soil organic matters supply the nutrients essential for plant growth in organic farming. However, in general, the mineralization rates of soil organic matter is slow both in humid tropical and humid arid region (Fernández et al., 2006 and Mary and Sanchez. 1990.). Therefore, to establish and maintain soil organic matter content to a certain level through the continuous application of compost can be effective strategies in organic farming. However, climate and soil significantly affect the accumulation and storage of organic matter in the soil because of the interactions of temperature and moisture on plant productivity and the ability of the soil mineral components to retain organic matter. Under tropical and subtropical climatic conditions, due to high cultivation frequency, and a low input of the organic matter content in the farmland soil generally it is common for the soil organic matter content to be lower than 20 g kg −1 (Huang SN 1994). 

The biological component of soils usually responds more rapidly to changing soil conditions than either the chemical or physical properties (Forge et al., 2008 and Kukreja R and Meredith S 2011). Soil enzymatic activities have been used as indicators of soil fertility because they are a reflection of the effects of cultivation, soil properties and soil amendments (Pokharel et al., 2015). Thus this study was designed with formulated organic compost rich in biologically active compound with locally available natural elements including cow dung, compost, was applied in agricultural land to estimate the land fertility and crop yield. During the study period routine analysis of available chemical nutrient in the field was performed to determine the nutritional condition of fields.